1. Field of the Invention
The present invention relates to a sleeve connector for joining optical fibers retained by ferrules in close or contacting relationship, and, more particularly, to a sleeve-shaped optical fiber connector that is formed with perforations arranged in a given pattern so as to be elastically deformable in a radial direction.
2. Description of Related Art
Many optical fiber connector designs in use today in telecommunication technology contain precision cylindrical ceramic or glass ferrules that are mounted in an optical fiber connector in order to join optical fibers for signal transmission. Bare ends of optical fibers are bonded in close fitting axial bores in these ferrules and the ferrule tips are polished to provide low insertion loss and back reflection connection. The connector used with the ferrules are formed in the shape of split sleeve. One of the central functions of such a split sleeve connector is the centering and aligning the ferrules. Alignment of the ferrules is essential in the standpoint of bringing the centers of the optical fibers into alignment in order to provide low insertion loss. Another central function of the split sleeve connector is to provide appropriate force for clamping the ferrules, in other words, to allow the ferrules to be pull out with intended drawing force.
There are, at present, many different types of split sleeve connectors in use, all of which are aimed at achieving clamp of ferrules with desirable force, as shown in FIGS. 10(A) and 10(B) by way of example.
FIG. 10(A) shows one of conventional split sleeve connectors 1 having a single axial slit 1xe2x80x2 along the entire length. The split sleeve connector 1, that is made of metal or zirconia, is formed by slitting a cylindrical metal or zirconia sleeve along its entire length or by pressing a metal sheet to a cylindrical configuration having a longitudinal slit. Considering the split sleeve connector in terms of clamping mechanism, the split sleeve connector 1 is elastically deformed symmetrically with the center axis of the split sleeve connector 1 by a ferrule or ferrules when the ferrules are inserted into opposite ends of the split sleeve connector 1. The elastic deformation provides the slit sleeve connector 1 with radial restoration force as a clamping force against the ferrules and clamp ferrules. The split sleeve connector 1 changes in its internal diameter due to the elastic deformation, resulting deterioration of roundness thereof. This causes uneven surface contact between the internal surface of the split sleeve connector 1 and external surfaces of the ferrules, which is one of causes for misalignment between the ferrules, and hence optical fibers, in the split sleeve connector 1.
FIG. 10(B) shows another conventional split sleeve connector 2 having a plurality of, e.g. six in this example, axial slits 2xe2x80x2 arranged at regular angular intervals. These slits 2xe2x80x2 is beyond half as long as the entire axial length of the split sleeve connector 2 and extend alternately from opposite ends of the split sleeve connector 2. Specifically, the split sleeve connector 2 is formed three slits 2a that extend from one of the opposite ends of the split sleeve connector 2 and are separated from one another by 120xc2x0 intervals and three slits 2a that extend from another end of the split sleeve connector 2 and are separated from one another by 120xc2x0 intervals and from the slits 2xe2x80x2 extending from the one end o the split sleeve connector 2 by 60xc2x0 intervals, respectively.
The split sleeve connector with more than two slits arranged at regular angular intervals and extending alternately from the opposite ends thereof is insufficient in elasticity and, however, inevitably result in that the split sleeve connector changes its internal diameter, which leads to deterioration of roundness.
These prior art split sleeve connectors are undesirable for axial alignment of the ferrules retaining optical fibers positioned and maintained in butting relationship because of insufficient elasticity and a change in roundness, which results in a drop in light transmission efficiency.
It is therefore an object of the present invention to provide a sleeve connector formed with perforations that has an elastic region covering required elastic deformation.
It is another object of the present invention to provide a sleeve connector formed with perforations that is free from a change in roundness and provides uniform surface contact between ferrules mounted therein.
It is a further object of the present invention to provide a process of producing a sleeve connector formed with perforations using an electroforming process which realizes low production costs.
The foregoing objects of the present invention are achieved by a sleeve connector formed with perforations that is directly produced in the form of a metal tube on an electroforming mandrel using an electroforming process, The electroforming mandrel is made up from a conductive rod which has an external surface and an external diameter finished to those required for the sleeve connector and is formed with a non-conductive layer thereon so as to provide non-conductive segments identical in configuration with the perforations of the sleeve connector and arranged in conformity with the given pattern of perforations of the sleeve connector.
The sleeve connector formed with perforations can be provided with any elasticity, i.e., putting it the other around, required rigidity, as required by selecting the pattern of perforation arrangement, the configuration of perforation, the number of rows of perforations, the number of perforations, the aperture area ratio (a ratio of the total area of perforations relative to the entire surface area of sleeve connector), the thickness of sleeve connector and the like according to applications of the sleeve connector. As the sleeve connector causes all-round radial elastic deformation in its own elastic region which is different from elastic deformation caused in the conventional slit sleeve connector due to local expansion of a slit of the sleeve connector, the sleeve connector always maintains its given roundness and interior diameter with respect to ferrules. As a result, the sleeve connector joins ferrules, and hence optical fibers retained by the ferrules, in close or contacting relationship, without an error in axial alignment and holds them with stable and reliable clamping force.
It is quite easy to finish an external surface of the electroforming mandrel to a diameter and surface texture as compared with finishing an internal surface of a hollow cylindrical tube to a required internal diameter and surface texture. The use of the electroforming mandrel formed with a number of electrodeposit sections for sleeve connectors makes mass production of the sleeve connectors with high efficiency and at low costs.